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O U R S P O N S O R S

October 10th, 2023

Kotlin Beginners Night

- What is Kotlin?

- Igniting your Android Journey

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Housekeeping

http://kotlin.wien

-XenableGarbageCollection

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News

Find us on LinkedIn�

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Community Interview

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1 Volunteer

7 easy Questions

Your favourite topic

In German or English

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Community Interview

Who are you in one sentence?

How long have you been working with Kotlin?

What are you working on (in Kotlin)?

How is Kotlin used in this project?

Tell us about a Kotlin win.

Tell us about a Kotlin fail.

Any problems/wins using Java Libraries?

Kotlin Frameworks / Features:

Arrow
AtomicFu
Coroutines
Exposed
Gradle DSL
HTML DSL
Kodein
KotlinX-IO
Kotlin Serialization
Ktor
Ktorm
MockK
TornadoFx

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otlin

Introduction for Programmers

Rohini Wani & Rainer Kern 2023

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Covered Topics

Brief History and language Evolution

Kotlin Syntax and features:

Variables, Type Inference and Control Flow

Nullability

Class Declaration and Data classes

Object Declaration

Functions (Top level, Extension, Higher Order, Default arguments)

Functional (Single Abstract Method) Interface

Smart Casts

Destructuring Declaration

Kotlin X Serialization

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What is Kotlin?

Kotlin is a statically typed general purpose language which supports both functional and object oriented programing paradigms. Kotlin compiles to Java Bytecode and runs on the JVM with full bidirectional interoperability and it can also be compiled to Java Script as well as running native.

The Interoperability of Kotlin and Java brings complete Java ecosystem to your disposal. Kotlin allows you to use every Java library and vice versa Kotlin libraries can be used by Java. The interoperability is almost 100% bidirectionally with one notable exception being Kotlin’s default arguments and named arguments, which cannot be used by Java as they do not exist in the language - at least not yet.

Lika Java and C#, Kotlin is statically typed with its type system also supporting global type inference so Kotlin often looks as concise as dynamically typed languages.�Kotlin’s typing system even goes further and includes nullability and mutability which both are validated by the compiler to prevent even more types of errors.

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“Hello World”

Statically typed, hybrid programming language

Runs on the JVM with full bidirectional interoperability

Runs natively on Android (generates 1.6 Bytecode)

Possibility to compile to Javascript using LLVM

Kotlin Native for iOS, MacOs and Windows

Developed by Jetbrains

Open source compiler and tools

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What is Kotlin?

Kotlin is a statically typed general purpose language which supports both functional and object oriented programing paradigms. Kotlin compiles to Java Bytecode and runs on the JVM with full bidirectional interoperability and it can also be compiled to Java Script as well as running native.

The Interoperability of Kotlin and Java brings complete Java ecosystem to your disposal. Kotlin allows you to use every Java library and vice versa Kotlin libraries can be used by Java. The interoperability is almost 100% bidirectionally with one notable exception being Kotlin’s default arguments and named arguments, which cannot be used by Java as they do not exist in the language - at least not yet.

Lika Java and C#, Kotlin is statically typed with its type system also supporting global type inference so Kotlin often looks as concise as dynamically typed languages.�Kotlin’s typing system even goes further and includes nullability and mutability which both are validated by the compiler to prevent even more types of errors.

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YAJL - Yet another JVM Language!

Jetbrains is a well known company with good tooling support

Nothing really new - just the best of all of them

It’s about the Java ecosystem not the language

It’s (1..6).forEach{ println("very") } easy to learn

Feels like Java 2.0 (Java on steroids)

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log -pretty --date=short

2010 Start of Development by JetBrains

2012 Open Source under Apache 2

2016 Release of v 1.0 in Feb

2017 Android Native

2019 v. 1.3.52

2022 v. 1.7.10

2023 v. 1.9.10

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The Kotlin Project started in 2010 was unveiled to the public in the next year - 2011. After it was open sourced in 2012 the first official release happened 6 Years later in 2016.

It was then quickly adopted as a first class citizen on Android, which gave the adoption rate a huge push.

Currently we are at v 1.3 which has been released in October and has brought some new features like coroutines.

Many people now think that Kotlin is a language only for Android - but this is by far not true. Kotlin can be used whenever you have used Java before. I myself have implemented a number of backends in Kotlin already.

Since Kotlin not only has the JVM but also Javascript and Native as target platforms it is already possible to write a complete full-stack application entirely in Kotlin.

Oh Yeah as a little inside joke for Java developers - Kotlin is also an island

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Introduction to Kotlin

Syntax similar to JAVA / C#
Expressiveness makes more readable.
Conciseness makes more understandable.
Flexibility - It allows developers to declare the functions at the top level
No static declaration (can cause problems to Java devs)
Has Coroutines

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// Java

public final String foo = "bar";

// Kotlin

val foo = "bar"

// Java

System.out.println("bar");

// Kotlin

println("bar")

package com.systemkern.demo

fun main(args: Array<String>) {

val name = if (args.length > 0) args[0] else ”Kotlin”

println("Hello $name")

}

Kotlin syntax is generally similar to Java, C# and other C based languages, tough it is much more expressive and concise or as I like to say it is much more clutter free. There is almost no boilerplate code to fill up you source files, the code that is there is much less redundant, optical distractions like multiple braces and semicolons are optional and discouraged.

Take this example, a simple public immutable String which is initialised with a value.

In Java (click)

And in Kotlin (click)

Another example is this (click)

How often have you typed this?

Much nicer - huh?!

These are two of the simplest example but you can already see the philosophy - there is nothing that I as the user of the language do not need - especially not those semicolons which always seem to go missing anyway?

No ritual writing of code just for the compiler. But actually writing more human readable code.

The last example I have here is to show some of the differences which we will go into later on.

This is a simple hello world program implemented in Kotlin

Let us see how many differences to java we can spot

There is no class - the main function is a top level function at the package.
There is no special syntax for Array. It uses exactly the same syntax as lists and sets do
if - else can be used as an expression. In our case that saves us at least one LOC
At last we have string templating - variables can easily be put into strings by using the $ operator

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Syntax

kotlinlang.org/docs/reference

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Defining Variables

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Language Features

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Type Inference

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Nullability

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Nullability (2)

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Class declaration

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Object Declarations

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Pojos

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Pojos (2)

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Explicit Properties

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Idiomatic Properties

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Data Classes

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Data Classes (2)

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Multiple Classes per File

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Simple Application

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Top Level Functions (like in JS)

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Default Arguments

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Infix functions

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Higher Order Functions

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Extension properties

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Extension Properties (2)

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Extension Properties (3)

In the object oriented world, these extension functions and properties are insanely powerful

but ...

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More Smart Casts

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More Smart Casts (2)

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More Smart Casts (3)

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Deconstructing Data Classes

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Collection Api

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Kotlin @ Google IO 2017

youtube.com/watch?v=X1RVYt2QKQE

Try Kotlin Online

try.kotlinlang.org

Learn Kotlin

kotlinlang.org/docs/tutorials/koans.html

Kotlin Vienna User Group

kotlin.wien

Talking Kotlin podcast

Talkingkotlin.com

kotlinlang.slack.com

https://surveys.jetbrains.com/s3/kotlin-slack-sign-up

KEEP (Kotlin Evolution & Enhancement Process)

https://github.com/Kotlin/KEEP/issues

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Igniting Your Android Journey:

Exploring the Realm of Mobile Development.

Jeremiah Polo

Android Developer

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Covered Topics

Introduction to Android
Setup developer space
Android Basic
Future of Mobile (KMM)
Seeking help and resources
QA

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Introduction to android

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Why Android

Open source : For the curious, access the source code of Android OS. �
Large consumer base: Android runs on 3B+ active devices, as of 2021 �
Easy penetration to the market. Play Store reviews takes a small amount of time as compared to Apple Store.

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Why Android

Earn from it: As a developer, business subscriptions…

Easy to learn: Great amount of free courses, tutorial and guides from the source (Google)

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Setup development space

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Android Studio

The official Integrated Development Environment (IDE) for Android app development.
Integrated with Syntax highlighter, Emulator, e.tc…
Required JDK( Java Development Kit) - Provides the environment and tools to develop application that run on java virtual machine (JVM)
Required Android SDKs: Collection of tools and libraries for android development. .

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Android Basics

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Android Developer tools

UI	Logic	Build Config
Kotlin	Kotlin	Kotlin Scripts (Kts.)
Java	Java	Groovy
xml

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Android Project Directory

App directory

Manifest
Java
Res

Gradle

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Android Project Directory

App directory

Manifest
Java
Res

Gradle

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Tools and Language

Kotlin -> UI and Logic
Xml -> UI
Gradle -> Build process

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Components of Android Application

Activities
Services
Broadcast receivers
Content Providers

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Demo on Compose + Kotlin

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Android App Development lifecycle

Planning/ �Inception

Design

Development &�Testing

Deployment

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Planning / Inception

Requirement gathering

Shortcomings and mitigations

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Design

Design phase on how the app will/ should look like

Considering Material Design : Provides look and feel guides to making android applications

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Development and Testing

Implementation phase
Transferring the concept from design to code(Look and feel)
UI logic -> Interaction
Testing

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UI

Composables

Layout

Events

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Data

Repositories

ViewModels

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Testing

Logic

UI

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Deployment & Monitoring

Providing the app to the users (Play Store: )

Internal testing
Open testing
Production

- Manually or using use of automation tools

- Fastlane, Github Action, �- Monitoring how the app performs. � - Crashlytics

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Future of Mobile development

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Kotlin Multi Platform

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Kotlin Multi Platform

1 Language to rule them all
Sharing code between platforms
Native capabilities: Ui in compose + Swift
Faster development

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Demo on KMM

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Next Steps

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Keep building

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Keep building

Start a project/projects

Personal tool, game.

Share what you build
Deep dive into the tools
Material design
Explore courses, blogs and tools

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Engage in the community

Join community forums like Stackoverflow, github.
Attend meetups: virtual or physical. Network to get opportunities like internship mentorship

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Keep learning

Official android developer resources
Tech news e.g Kotlin weekly
Engaging with people from community
Keep learning

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Seeking help and resources

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Source: Google Developer Relations

Google developer guides (https://developer.android.com/guide)
Mad skills videos (https://www.youtube.com/playlist?list=PLWz5rJ2EKKc91i2QT8qfrfKgLNlJiG1z7)
Android codelabs(

https://developer.android.com/courses/jetpack-compose/course)

Google Samples (

https://developer.android.com/jetpack/compose/samples)

@AndroidDevelopers youtube

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Community

Android heads
GDG Vienna
Kotlin Vienna
Twitter #AndroidDev
Droidcon

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Blogs

Kotlin Weekly

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Courses

Developing android application with kotlin @udacity (https://www.udacity.com/course/developing-android-apps-with-kotlin--ud9012)

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Q.A

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Sources

3 Billion active devices (https://twitter.com/Google/status/1394719458921431040)
Android vs iOS Market share (https://www.bankmycell.com/blog/android-vs-apple-market-share/, https://gs.statcounter.com/os-market-share/mobile/europe )
Android Studio(https://developer.android.com/studio)
JDK (https://www.oracle.com/java/technologies/downloads/)

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Sources

3 Billion active devices (https://twitter.com/Google/status/1394719458921431040)
Android vs iOS Market share (https://www.bankmycell.com/blog/android-vs-apple-market-share/, https://gs.statcounter.com/os-market-share/mobile/europe )
Android Studio(https://developer.android.com/studio)
JDK (https://www.oracle.com/java/technologies/downloads/)

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Upcoming Schedule 2023

Oct: DevFest Vienna 14th October

Oct: Java Vienna: "distributed workload 23rd October� scheduler with Kafka" & TBA

Nov: Androidheads Vienna: Meet up 2nd November

Nov: Java Vienna: "Keycloak.X & quarkus" & 13th November� "Java containerization deep dive"

Nov: Domain Drive with Kotlin @ openDEVS 14th November

Dec: Weihnachtspunsch powered by APSA 12th December

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Contact us

If you have any questions or want to get in touch with us, you are more than welcome to do so!

Our contact information:

meetup@kotlin.wien

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